1. Field of the Invention
The present invention relates generally to centrifugal superchargers for providing increased airflow to an engine. More particularly, the present invention concerns an improved transmission lubrication arrangement for effectively lubricating the transmission components that drivingly connect the impeller to the power source, without having to tap into the lubrication system for the engine and without limiting the transmission speed.
2. Discussion of Prior Art
Centrifugal superchargers are traditionally provided with an internal step-up transmission that serves to rotate the impeller significantly faster than the input shaft connected to the engine. It is particularly known to provide a centrifugal supercharger with an internal belt drive supported by prelubricated (e.g., grease-packed) bearing assemblies. Although this type of transmission eliminates the need for lubrication (except for that already provided with respect to the bearing assemblies), it is believed to have relatively low operational limitations that effectively prohibit the supercharger from generating large amounts of pressure increase and airflow. On the other hand, a number of conventional centrifugal superchargers, particularly the higher boost models, utilize a gear drive that must, along with the bearing assemblies supporting the gear drive, be continuously lubricated during operation. Those ordinarily skilled in the art will appreciate that gear-type transmissions generally have greater structural integrity and are able to transfer significantly more load than a belt-type transmission. However, a gear-type transmission typically requires dispersion of lubrication fluid generally throughout the transmission chamber.
In the past, such a lubrication requirement has been problematic. First, lubrication fluid is commonly supplied to the transmission chamber of the supercharger from the engine. This almost always requires a fluid line to be tapped into the oil reservoir of the engine, which is often considered highly undesirable. It might be possible to alternatively provide a separate lubrication reservoir dedicated solely to the supercharger, although such a circulating arrangement would obviously be costly and consume a considerable amount of valuable engine compartment space. With respect to either alternative, the manner in which lubrication fluid is typically directed to the transmission components (e.g, jets, wicking arrangements, etc.) is believed to be unreliable, ineffective and/or in other ways problematic.
There are also xe2x80x9cself-containedxe2x80x9d friction ball driven (e.g., Bendix drive) superchargers. That is to say, a number of superchargers wholly contain the lubrication fluid therein. Those ordinarily skilled in the art will appreciate that the transmission chamber of such a supercharger is typically filled with lubrication fluid. It has been determined, however, that a fluid-filled transmission chamber actually reduces the load capacity of the supercharger, as a result of the significant hydraulic separation forces caused by flooding the transmission and bearing assemblies. Furthermore, this type of construction adds heat and fails to provide sufficient cooling of the transmission.
Responsive to these and other problems, an important object of the present invention is to provide a supercharger that is capable of providing relatively high amounts of airflow (e.g., 1800 gasoline horsepower). It is also an important object of the present invention to provide a supercharger that is self-contained, such that the lubrication system for the transmission is confined to the supercharger itself. In addition, an important object of the present invention is to provide a transmission lubrication configuration that has virtually no limiting effect on the boost provided by the supercharger. Another important object of the present invention is to provide a supercharger having a gear-type transmission and an associated lubrication system that assuredly provides sufficient and effective lubrication to the transmission components. Yet another important object of the present invention is to provide a supercharger having a durable, simple and inexpensive construction.
In accordance with these and other objects evident from the following description of the preferred embodiments, the present invention concerns a supercharger having a case that defines a compressor chamber and a transmission chamber. The rotatable impeller in the compressor chamber is drivingly connected to a power source (e.g., an engine) by the transmission. The transmission chamber includes a fluid reservoir portion in which lubrication fluid is located, and at least part of the transmission is located within the transmission chamber but outside the reservoir portion. A fluid-propelling element serves to propel lubrication fluid from the reservoir portion of the transmission chamber to the part of the transmission. This configuration consequently permits the supercharger to be entirely self-contained, with the lubrication fluid being located entirely within the transmission chamber. Furthermore, the part of the transmission outside the reservoir portion is not subjected to significant hydraulic separating forces, which would otherwise be produced if it was submerged. Moreover, the fluid-propelling element is preferably arranged to create a fluid mist within the transmission chamber. It is believed that such an environment ensures effective and reliable lubrication of the transmission components.
The present invention also contemplates utilizing a rotatable component of the transmission as the fluid propelling element. The component projects into the reservoir portion of the transmission chamber and slings lubricant to the part of the transmission located in the transmission chamber but outside the reservoir portion thereof. In the preferred embodiment, the rotatable component comprises the relatively low speed drive gear provided on the input shaft of the supercharger.
Other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiment and the accompanying drawing figures.